1. Field of the Invention
This invention relates in general to the field of optical scanning, and in particular to the field of optical scanning of items carrying an identification code.
2. Description of the Prior Art
In known prior art flying spot X scanning systems shortcomings are encountered in the detection of the code carried by the item being scanned. Particularly, in the scanning of the Universal Product Code (UPC), which is a bar code particularly adapted for the grocery industry, difficulty is encountered in the detection process using X scanners because of the wide variety of contrasts and wide range of scattering co-efficients associated with the different packaging materials used in this business. Some of these packaging materials such as glass, plastic and cellophane wrapped items produce specular reflections which are reflections wherein the angle of incidence equals the angle of reflection. Specular reflections are harmful to the detection process because these reflections tend to saturate the photo-multiplier detector so that a reading cannot be made of the code being scanned. This is a troublesome problem since the clerk in a grocery store must repeat the scanning by re-orienting the item carrying the code and again drawing it across the scanning aperture. Several scans may be necessary before a successful one is obtained. This additional scanning detracts from the desirable features of speed and ease of operation which are desired characteristics of optical scanning.
Another shortcomimg of the known prior art is that it is difficult to raise the emitted laser light source power above a certain level while still complying with federal regulations of the Bureau of Bioligical and Radiological Health (BRH). Laser power often must be raised to an excessively high level in order to get an adequate reflection from a low contrast UPC code label. Therefore, if the prior art devices were to raise their laser power source while still complying with the BRH requirements, very sophisticated monitoring devices would have to be incorporated to see how much energy had actually been radiated. Accordingly, if that level of radiation had been radiated. Accordingly, if that level of radiation had been exceeded, the scanning equipment would have to be shut off for a certain amount of time before it could be turned on again. The monitoring equipment which would be required would be an additional piece of equipment that not only adds much additional expense to the scanner device, but in addition complicates its operation.
Another shortcoming of the prior art is that the data or reading rate is too slow. A slow reading rate decreases the performance of the scanner system and prevents it from becoming a viable product in the market place.
Therefore, in the light of the above discussion, the prior art is limited in solving the problems above discussed.